Lubricants, especially solid film prelubes, are utilized in several metalworking operations. These metalworking operations can include stamping, drawing, forming, bending, rolling, cutting, grinding, punching, sawing, hobbing, reaming, spinning, extruding, trepanning, coining, swagging, and the like. The present invention concerns the use of solid film (dry film) prelube lubricants for such type of metalworking operations, utilized on ferrous and non-ferrous metals used to make containers which come in contact with food and beverages. Most often food and beverage containers are composed of either stainless steel or one of a variety of aluminum alloys. The term, press working operation, is used to define all mechanical processes where sheet metal is formed into specific shapes by the use of mechanical presses. Such operations can further be categorized as stamping and drawing. The term, stamping, is further used to describe all forming operations where parts are formed from sheet metal and there is no change in the gauge or thickness of the sheet metal. The term, drawing, is further arbitrarily divided into shallow drawing and deep drawing. Drawing defines all forming operations where there is a change or reduction in the gauge or thickness of the sheet metal. Shallow drawing can be defined as to the forming of a cup or shape no deeper than one-half its diameter with only small reductions in the metal gauge or thickness. Deep drawing can be defined as to the forming of a cup or shape deeper than half its diameter with substantial reductions in metal thickness or gauge. Formed food and beverage containers may be produced by one or a combination of these three fundamental fabrication metalworking operations.
Forming lubricants, especially solid film prelubes, facilitate these operations by reducing the friction that occurs between the sheet metal being fabricated and the tooling employed for the forming operation. By reducing the coefficient of friction for the specific forming process, power requirements, tool wear and heat generated during forming operations are all diminished. Heat significantly can affect forming operations by changing metallurigical properties of both the metal and tooling. It physically degrades these elements, causes their staining or oxidation and also creates physical and chemical changes in the lubricant affecting its performance. In addition, blocking or adhesion between the sheet metal and tooling is reduced or eliminated during the forming operations, transit and storage of the formed parts.
The prevention of blocking or adhesion between the sheet metal and tooling is of extreme importance. In addition, the use of specific metalworking forming lubricants such as solid film prelubes significantly can reduce or eliminate the production of scrap parts (formed parts rejected due to physical damage) which may result from the failure of some forming lubricants.
Solid film prelubes have been proven to work in virtually any drawing or stamping operation, it simply being a necessity of correctly matching product chemistry and coating weights with the application. They have not been used in the drawing containers used in a variety of applications where incidental food and beverage contact may occur between the contaminated container and the actual food or beverage product. All of these containers, for example, (food containers such as cans, bakeware, baking containers used in process) would normally be thoroughly cleaned in aqueous acid or alkaline cleaners following forming before being sent to their actual application. This is normally done to remove any and all traces of lubricant in order to provide a clean container. Furthermore, such containers could be exposed to further processing such as the application of organic coatings. Thus, if trace amounts of lubricant were to remain following cleaning, situations might arise where incidental food or beverage contact could occur. Trace amounts of lubricants could also impact on the adherence of organic coating. This could lead to potential contamination. A variety of lubricants are currently used to form these types of containers. They are all liquid lubricants and generally are composed of blends of hydrocarbon oils, vegetable oils and additives. Many of these products are not FDA approved for incidental food contact. In additions, these products often are only satisfactory lubricants depending upon the severity of the forming operations. Large quantities of parts will often be rejected due to surface defects or metal ruptures due to improper lubrication. These lubricants are also often applied at high coating weights, following the adage that more oil will lubricate better. The advantages of a solid film prelube formulation is that it offers several benefits over current products:
1. All components would be FDA approvable for incidental food and beverage contact eliminating the worry associated with health concerns if contamination did occur. PA1 2. It would offer substantial improvements in lubrication over the current regime of products being used, reducing or eliminating scrap parts. PA1 3. Furthermore, it would offer some of the other benefits associated with solid film prelubes, namely the elimination of inhouse lubrication systems (chemical and drum storage) and significant reductions in coating weights currently being applied. 25-350 mg/ft.sup.2 could be used versus 500-1500 mg/ft.sup.2 currently being used for hydrocarbon-based lubricants. PA1 4. Such a product should also offer excellent long-term corrosion protection for metal coils or blanks stored in-process prior to forming, cleaning or finishing. Furthermore, the product should be removable, cleanable and compatible with the existing aqueous cleaners being used to process current lubricants.